IANAL, but it seems to me that as long as it's for your personal use only and you don't share the web page thus created with a public audience, it's harmless or at the very least could easily be argued as fair use.
You certainly wouldn't want to make the generated pages public though...
"Non sequitur. Your facts are un-coordinated." - Nomad

Having dealt with a number of cartoonists, I'd have to agree with Clownburner...most cartoonists don't particularly care if you create something for personal use, but it is incredibly difficult these days to offer cool content without being killed by your own popularity.

Basically, if you put up something cool on the web and lots of people come see it, then you've got to spend money on bandwidth...in order to cover some of that cost and maybe expand what you are doing, you allow some advertising on the pages that people are visiting. If you start having a whole bunch of people using a grabber that gets rid of the ads on the cool stuff you find on the web, then shortly the cycle reverses...the bandwidth isn't covered by the advertising, the cartoonist can't cover his/her costs and the strip shuts down. You, the fan, lose out, because you weren't getting the advertising on the site.

It's one of the basic flaws of the internet right now...and one of the reasons that micropayments and subscriptions are going to come about sooner or later - nothing in life remains free.